The proposed research is designed as a three-year investigation to study factors which influence substrate uptake, (glucose and fatty acid) by the isolated-perfused rat lung. These will include the influence of altered circulating substrate levels, influence of pulmonary flow and pulmonary pressure, and the influence of nonperistaltic flow on substrate uptake. In addition to substrate uptake, lactate, pyruvate, and ATP levels will be measured. Lungs will be perfused for 1 hour with a medium containing washed bovine RBC's resuspended to a 15% Hct with Krebs-Henseleit bicarbonate buffer - 5g% bovine serum albumin. Ventilation will be accomplished with a 95% 02 - 5% C02 mixture with a V of 160 m1/min. Net uptake of substrates will be calculated as a product of arterial-venous concentration difference and perfused volume.